DESCRIPTION (Adapted and modified from applicant's abstract): Trichomonosis is the number one sexually transmitted disease: an estimated 10 million women in the United States and 250 million women worldwide are expected to be infected during the coming year. Infection with Trichomonas vaginalis has major consequences for women's health, including predisposition to HIV infection, associations with cervical cancer, and complications of pregnancy (premature membrane rupture, preterm delivery, and low birth weight). The long-term goal of this research team is to understand the pathogenesis of trichomonosis. The objective of this particular application is to understand the molecules and mechanism(s) by which T. vaginalis recognizes and binds to vaginal epithelial cells for host parasitism. Cytoadherence by this parasite is an important first step for infection. The rationale for undertaking such studies is that such an understanding will lead to a strategy for interference of infection by preventing the key first step in infection. The central hypothesis to be tested is that specific T. vaginalis cytoadherence to the vaginal epithelium occurs via four surface proteins (adhesins), each of which is encoded by a multi-gene family, and that the expression of these adhesins is regulated by a combination of parasite, host and environmental factors. The current working model is that optimal cytoadherence results from i) the coordinate expression of adhesin genes, ii) the placement of the four adhesins on the parasite surface, and iii) the association of each adhesin with a distinct receptor on the host cell surface. During the proposed funding period the three specific aims to address this hypothesis are: Aim 1. To evaluate the relative contributions of each of the candidate T. vaginalis adhesins thus far identified for its role in cytoadherence of organisms to vaginal epithelial cells. The proposed studies will determine the extent of expression of the candidate adhesins on individual organisms and whether each of the four is equally important in adhesion. Dr. Alderete will also express the recombinant proteins in E. coli and determine the extent of their identity with the natural proteins isolated from T. vaginalis. Aim 2. To characterize the host and environmental factors tha| regulate the synthesis and surface expression of the different T. vaginalis adhesins. Dr. Alderete will determine which environmental signals, focusing his attention on the known role of iron in addition to host cell contact, pH and hormones, influence adhesin synthesis and surface expression. Quantitative approaches will be employed to confirm and extend the concept of iron and vaginal epithelial cell contact directed up-regulation of adhesin gene expression. Aim 3. To identify specific non-coding gene sequences that contribute to regulation of expression of the T. vaginalis adhesins. These experiments will determine the 5N genomic and 3N transcript untranslated regions (UTRs) and analyze regions of the genes for their role in regulating the half-life of the adhesin transcripts.